text:
Is it safe to takeoff with some ice and snow on the wings?
I took a look at the post 'What things can a passenger look out for, to indicate an emergency?', and remembered this video I've seen.

Obviously, video uploader claims that this take off was unsafe due to some ice and snow on the wings. Was he right? Were the pilots really breaking any regulations?

It's important to remember that whether a given condition is safe or not is really not a binary choice. Think of "safe" being a probability index along a line starting with zero on the left being "this airplane is certainly not going to be able to fly" and 1.0 on the right being "this airplane is certainly going to fly. While that index can be zero, it will never be 1.0 but can only approach 1.0. And remember that in third world countries, operators are often willing to fly with a lower such index than might be used in so-called first world countries.

It appears that there was a considerable amount of contamination, either snow, ice, frost, or a mix thereof, on the wing when the takeoff roll started, and that is not considered safe under any current standards I'm aware of.
There are markings on the top of the wing for the 737 Next Generation series that define an area where cold-soaked fuel frost is acceptable up to a defined thickness, but the area covered by the contamination in the video extended beyond those markings, so even if it was CSFF (which I doubt, given what's shown late in the video), it was still more than what's allowed.
Late in the video with the aircraft flying, we see that much of the ice is no longer present, which means that it detached from the wing at some point.  If it was dry snow that blew off in the first 10 or 20 knots of the takeoff roll, that's no big deal, but you don't see the ice gone until late in the video -- this isn't simply dry snow.  Plus, you still see significant patches of ice adhering to the wing at the end of the video -- which suggests that it isn't CSFF nor dry snow, but ice.
The current accepted standards of safety in commercial aviation don't permit taking off with any ice adhering to the wing, and from what is shown in the video, it certainly looks like that's what was done here.  (Disclaimer, I'm no expert on watching u-tube videos of ice-covered wings, so there may be more going on here than is apparent on first or second viewing.)  IF that's correct, then I'd have to agree with the title of the video, that this was unsafe.
The standards of safety allow for a lot of margin, so that when mistakes get made they are still likely to be survivable, and it looks like that's how things turned out here.  Things were done wrong but everybody made it out okay.  But... what if one more thing had gone wrong?  What if they'd lost an engine at rotation?  Would the aircraft have been able to climb out with one engine & the wings in this condition?  Or would these guys have been headline news of a crash out of Sarajevo that killed all on board plus how many more on the ground?
No, this looks pretty far out of bounds to me.

The video appears to show frost or ice on the wing of an airliner during takeoff. Normally this is discouraged because even a thin coating of ice can disrupt an airfoil's boundary layer airflow, causing a premature aerodynamic stall and dramatically increased functional drag.
However, extenuating circumstances often intrude upon standard safety margins. There are many reasons why a flight crew might risk flying with an apparently contaminated wing surface:

The flight crew had hand inspected the wing and found it smooth even if discolored.
No de-icing was available.
De-icing was available but the takeoff waiting line was so long that the wing iced up again while taxiing. This was the minimum amount of ice that the flight crew could get the plane to the takeoff point with.
The captain is a right bastid and ignored the tearful pleas and terrorized screams from his first officer.
The discoloration on the wing is not ice or frost, but de-icing fluid.
Anything is safer than hanging about on the ground at Sarajevo Airport.

In any event, you are survived to tell the tale, so by definition the flight crew's judgement was correct.

Unless mortars were falling at the airport, none of those extenuating circumstances justify what that crew did.  If no deicing is available, or the line is long, or ice keeps reforming, you don't go.  Landings are mandatory, but takeoffs are optional, and if you can't take off safely, don't take off.  Simple as that.  Smooth ice is still ice, not safe.  Deicing fluid is either clear (Type 1) or green (Type 4) so that it does NOT look like ice -- and it would shear off during the takeoff.  And surviving a stupid decision, doesn't make the decision less stupid. They dodged a bullet.

"100% of passengers didn't die" is a pretty minimal standard for evaluating a crew's judgement. I think there's a lot we can't tell just by watching the video, but surely it is possible for a crew to exercise poor judgement without killing everyone on board. It's supposed to be about margins of safety and good decision-making, not "everyone didn't die so it's all ok."

Though others obviously disagree, I upvoted the answer. I found it realistic (though a bit colorful) at least insofar as the conditions I encountered in the 30 years of flying I did, and especially the last 12 years going into third-world countries. I retired in 1999. Perhaps things have changed. I hope they have. I think it important that Mr. Breveleri is not advocating operating with reduced safety margins, but recognizing real world conditions that perhaps influenced the captain's decision.

"100% of passengers didn't die" is the gold standard. All serious professional fliers aspire to this level of performance.

No, it's not.  A pilot aspiring to "I didn't kill anyone today" is not a professional.

While I agree that not killing anyone is important, it is also beneficial if the airplane comes down in as few pieces as possible. There is more to good piloting than not killing passengers. I personally always want to have an option B when I fly.

@Terry  would it have made a difference if the plane was a passenger plane instead of a cargo plane?

@dalearn That's a matter of opinion. Mine is, no, in general. I like that saying that goes something like, "get yourself there safely, and whatever is in the back will get there safely." There are certainly minor differences. Boxes don't complain about turbulence, so I rarely bothered trying to find smooth air in freighters. And, if you just ditched or are down and may burn, no point in the captain going through the back to ensure all pax are off if it's a freighter.


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Do financiers request IDERA's for small aircraft?
Do financiers request IDERA's for small aircraft, or just large ones registered under the CTC?

Welcome to aviation.SE! It might be helpful if you can explain what IDERA and CTC are.

Firstly just a little bit of background. IDERA's - Irrevocable Deregistration and Export Request Authorizations - are issued under the Cape Town Convention (or Cape Town Treaty). This is a voluntary convention that countries can subscribe to. It essentially provides more assurance for financiers, who can therefore provide lower interest rates to aircraft buyers.
The FAA states the eligibility requirements  for IDERA's, which, for fixed-wing aircraft, need to be able to carry at least 8 people, or can carry goods in excess of 2750 kilograms (6050 pounds). So most aircraft considered 'small' probably would not be covered.

source: Stack Exchange

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Why did the MSA for Taipei (RTCP) change?

I got a question about the Minimum Sector Altitude (MSA) on Jeppesen arrival plate (RCTP 20-2). The MSA circle  was divided into three sectors with three altitude before (2008, top image), but I found that it is only one altitude (not divided anymore) on the new version.
I've been looking for the reason for a long time but still can't figure it out. Does anyone know why they did such the change?

I notice the airport elevation was also increased by two feet

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text:
Why can't flight management systems receive instructions directly from the controller?
If an aircraft's flight management system has auto pilot and auto thrust coupling, and it can make changes to the aircraft speed and direction along the entire route without pilot intervention, then why can't controllers just be allowed to make these changes directly without the need to ask the pilot to do it?
Pilots and controllers would still be monitoring the aircraft should things go wrong, but gone would be the days of endless voice instructions like "Flight xyz turn heading 123 climb and maintain...join the localizer for runway xx" "Contact xxxx on 123.xyz"
So many accidents happen due to misheard or unheard voice communication between pilot and controller, along with the pilot's misunderstanding of how flight director modes work.
The FAA should make this a goal, much like adoption of ADS-B.

The ATCO is not a pilot, is not in command of the aircraft... is not able to evaluate if this change can be accepted, or is feasible.

These types of data link messages are the goals of the NextGen airspace system being implemented by the FAA and others around the world. While it doesn't mean that ATC will fly the plane, it does mean that voice comms are replaced (augmented actually) by text links. This is one of the goals of the FAA, and ADS-B is part of that whole system.

Finally a reason to want to become a hacker for the CIA...

Because the pilot in command of the flight is responsible for the safe outcome of the flight, not air traffic control. Pilots are responsible to evaluate a clearance and accept or decline it. Controllers have very limited information on a flight's situation and circumstances, information the pilot(s) must be aware of and must take into account in accepting a clearance. Such information could include aircraft system status, fuel state, weather conditions, and passenger needs.
Pilots make mistakes, and so do controllers. A single controller handling multiple aircraft in his or her sector is not expected to have a full awareness of each aspect of each aircraft's situation. That is the job of the pilots. The pilots and controllers work as a team, but the ultimate responsibility rests with the pilot in command.

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What is the VOR reference signal?
What is the VOR (VHF Omnidirectional Range) reference signal?
I have to calculate the spectrum of this signal.

https://en.wikipedia.org/wiki/VHF_omnidirectional_range has a good description

@mins That's very helpful and complete documentation. The best answer! Thank you for finding time to help me.

See this answer, the reference is a 30 Hz sine, but depending on the type (CVOR/DVOR), the reference is transmitted either as a AM sideband (DVOR) or as a FM subcarrier at 9.96 kHz (480 Hz swing) sent as DSB-SC (CVOR). The other signal is the variable, also a 30 Hz sine. The corresponding spectrum is this one (missing the id tone and voice channel)

VOR Ground Station is aligned with magnetic North. It emits two signals:

a 360° sweeping variable signal
an omni-directional reference signal

When an aircraft receives those signals, its receiver compares those and a measures the phase difference. This gives a precise radial position of the aircraft which is displayed on its Omni-Bearing Indicator (OBI), Horizontal Situation Indicator (HSI) or a Radio Magnetic Indicator (RMI), or a combination of two different kinds.
This picture shows the two signals:

Blue is 360° sweeping signal
Green is omni-directional reference signal

This is very enlightening! And also I would like to know more about this omni-directional reference signal (blue one). For example if it is sinusoidal, and all other informations for calculating its spectrum. Thank you!

Trying to fig out why they made the reference signal flash in that gif. I guess that's indicating when it's at 0° phase?

@TomMcW: Yes it's misleading, it looks like the bearing is determined by timing the interval between a north pulse and the maximum strength of a supposed thin beam (and I saw another post on the site where it's interpreted this wrong way).


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Why do some aircraft have to have the landing gear pinned prior to towing?
The Phenom 300 require all three gear to be pinned before towing. I assume there are other aircraft with the same restrictions.
The nose gear is understandable, due to the link being pinned out of the way to allow a larger range of movement of the nose gear.
But why the main gear? Does it have something to do with the trailing link style of the mains?

The most direct answer is that gear pins are installed to prevent accidental retracting during towing. I'm not typed on the Phenom, but the landing gear actuators are most likely hydraulic. Even if they are electric, the airplane is expected not to have any form of power established during towing, making accidental retraction more possible, even if the gear is held in the down position by locks, not its actuators.
The requirement to install the gear pins is not related to the trailing link design. No matter what the design was, that requirement would be there for each gear.
This requirement is ubiquitous on larger aircraft. During airline operations, I have had an aircraft towed over to me many times. I have never seen a plane in tow, at least at my company, that did not have the gear pins installed during towing.

Great comment, I am a retired A&P and read this question yesterday but had forgotten about this. When I worked for Continental we only pinned the nose gear. But, I noticed aircraft that where having A/B/C checks had the mains pinned too. I also noticed most govt planes i.e FAA pinned all the gear when parked.

Pinning the gear, for airline aircraft, is much ado about nothing. The main gear can't retract, even with hydraulic pressure and commanded actuation, due to the over-center locks (the nose gear probably could). Consider, have you EVER heard of a towed aircraft have a gear retract? And even better, during towing typically only one hydraulic system is powered, for brakes.But during pushback, engines are being started, both systems are ready for pressure, and are the gear pinned? Nope. Pinned while parked & zero hydraulic pressure is even less necessary than while towing. Tradition, tradition...

They’re safety pins, installed not to prevent the gear from retracting while towing - the gear is designed to support the jet during much faster operations on the ground - but to prevent an accidental retraction when maintenance personnel are working on or under it.  Gear collapses have killed Mechanics in the past.


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How are backlit aircraft panels (for simulators) made?
I'm wondering by which method this sort of aircraft panel that enabling backlighting are made? What is the process? I've gathered they are acrylic but how is the gray paint selectively removed?
pic http://www.simparts.de/WebRoot/Store/Shops/15465782/4B72/6E37/0BF8/50E9/641B/C0A8/28BA/29AA/A320-OHP-009-5.jpg

Possibly laser etching? Great question btw, looking forward to seeing the answer.

@DannyBeckett  i was hoping you might have the answer to this one :/

Missed the "backlit" part in the title... I guess it's not laser then, I don't know the answer, I've only just started building mine... it just consists of a few switches so far!

same way other backlit panels are made perhaps?

Wipers?  Must be a fancy airplane :)  And I believe lasters are often used to remove that kind of stuff.

Heheh, rain repellant sounds like a force field.

It's a 3 layer color system with white opaque special laser colour, a black light block layer, and the final colour. For military it stays black without the 3rd one. After spray painting the special laser color is removed with a laser system. You can see it here.

This video says the following:

Here's my Tonson TS-3040C CNC making an EFIS panel for my flight
  simulator. For the lettering I am using a 0.4mm End Mill and for
  cutting out I'm using a 1mm End Mill. RPM is 10000 and movement is
  300mm / Min. The material is Cast Acrylic which I have given one coat
  of black paint and two coats of grey paint.

So that's at least one method, but there are probably more...

This page has some good information and a graphic, looks like the same as shown in the video Manfred posted. Clear plastic with an opaque layer that is engraved off, and lighted from beneath.


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What is a fair and unbiased method of measuring airline safety?
Here are a few thoughts:

'Real' accidents happen much too seldom to be of any real measure, and they would have to be compensated for the number of passenger kilometers as well to be objective. Large airlines may have be involved in more accidents, but they have more aircraft. Many airlines low down on the reports had accidents many years ago.
Avherald and the like may be good sources but emphasize that they don't report on all accidents.
Different jurisdictions have different reporting requirements.

What is a fair and unbiased method of measuring airline safety?

Smaller incidents (like brief loss of control or ATC violations) that would be especially important for evaluating smaller airlines may not be reported, especially internationally.

I think this question is too opinionated. In order to measure safety, you have to define what you mean by safety, which is subjective and opinionated. How do you compare different accident types, and how much weight do they count for when scoring safety? Do you factor in training programs, and if so, how do you judge them? How relevant is a crash which happened five years ago versus one that happened yesterday? Different people/countries/organizations will all have different opinions.

@BretCopeland Safety is not really subjective. It is inverse to the probability of injury or death. The problem is that safety is so high in airlines, that in order to quantify it by traditional statistics it would take a very long time to collect enough data to make a significant measure. During that time, the safety of the operation is unlikely to be constant and therefore safety essentially is not measurable by looking at accidents. ...

... Accepting that, looking for alternatives becomes a very academic exercise which will cover incident statistics, corrected for fleet and routes, operating environments etc. And then one could look at CRM/ culture, training, maintenance organisation etc. While I like the question (and upvoted it) for this academic side, it also think its too broad to be answerable here and that's why I vote to close it.

@DeltaLima you just defined safety as the probability of not being injured or killed, but that asserts that injuries and deaths are equal for measuring safety, and, in reality, they are not. So, how to you weigh minor and serious injuries against deaths? We understand the general premise of safety, but unless you strictly define it, it is up for interpretation. Generally, you would simply break up the things you care about and then calculate separate probabilities for them, but you can't rank airlines against each other unless you weight each probability, which is entirely subjective.

I agree with everything else you said.

I think the consensus is that, as written, this question cannot really be answered. I'm placing it on hold until it can perhaps be narrowed or made more clear what you're actually asking, simply because we don't want a bunch of opinion or "it depends" answers. Ironically, as an aerospace engineering student, you're likely in a better place to find an answer than the rest of us anyway.


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Just how inaccurate are (Las Vegas) VOR radials?
I was discussing VOR-based navigation with a pilot, and he mentioned that VOR doesn't provide a very high level of integrity and safety (at least, compared to GPS or DME). He explained that the FAA only guarantees VOR radials listed in approaches and claimed that "one quarter of the radials at Las Vegas are bad".
Are the Las Vegas radials off by just a degree or two or is it worse than that, and how did they get to be so bad? Is it a case of normal variation due to geography and magnetic drift, or is it something more serious like what happened in 2003 to an Airbus A-320-231, G-MEDA on approach to Addis Abeba Airport?

Thanks for the link to that nightmare fuel.

I guess it depends on what you consider to be a "high level of integrity and safety." VOR is a perfectly acceptable means of navigation if you know how to use it. And, I guess, if the transmitter hasn't been flooded.
Let's take a look at the data for the Las Vegas VOR:

Now, that does look like a lot of "unusable" radials, but it's not actually as bad as your friend claims. First of all, you're not "only" guaranteed service on legs of instrument approaches. You're also guaranteed service along Victor airways, and within a standard service volume. Think about it: certainly you can't expect to pick up the Las Vegas VOR in Florida. So where should you expect to be able to use it? The answer is on flight tested legs (approaches and airways) and within its service volume. According to the AIM, a VOR must "conform to flight inspection signal strength and course quality standards throughout the published SSV". The (H) after the VOR name indicates that Las Vegas is a high-altitude VOR. Let's look at its service volume:

Notice first that the service volume only has a radius of 40 NM to begin with at low altitude. Most of those cutout unusable radials reduce this to 35NM instead. So it's not that much of a cut. And above 16,500 feet? It's all usable, and that's where most of its service volume is. So in fact, the vast majority of the Las Vegas VOR's service volume is usable, that is to say, meeting FAA standards of signal strength and course quality.
Where it doesn't, it's usually because of terrain in the vicinity of the transmitter. As a radio signal, the VOR beacon bounces off of nearby hills and mountains.
Now, what does it look like to the pilot using the system if they're in one of those unusable regions and not receiving an adequate signal? VOR receivers are also FAA approved and if they are not receiving a strong enough signal with enough integrity, then they will display a flag. It should not present totally false data without a flag. The problem with your Ethiopian flight seems to be that the VOR transmitter was transmitting the wrong info, which of course the receiver can't know anything about and it did not flag.
That would be a pretty terrible scenario. That is not what is ever going on around Las Vegas. NAVAIDS in the USA are monitored for integrity. The worst that will happen in a receiver in Las Vegas will (hopefully) be a flag that indicates the receiver is not receiving an adequate signal.

Well thought out and useful answer.

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text:
How do you check for soft or muddy ground on a backcountry landing?
I've been curious about backcountry landings, but one part of the practice still seems to based more on instinct and experience than on well-explained processes.  I've read about making sure the strip is long enough, looking for power lines, avoiding campers and wildlife, checking your GA area, and other stuff, but what about mud?
Everyone seems to say that you do a pass close to the ground or a touch and go, but after that they seem to just make an educated guess based on how the ground looks and feels.  Given that a misjudgement here could be disastrous and prevent you from being able to accelerate to a take off, what's the actual process and list of things to consider to make sure you're landing in a good airstrip and not a foot of deceptive-looking mud?  Does a touch-and-go give you enough information or do you need to carefully consider things like recent rainfall, watershed shape, etc.?

Image from this video.

Usually, it's a combination of making a couple of low altitude passes over the landing site and visually observing the conditions of the terrain in the area and personal experience selecting a site based upon the knowledge of the local terrain and soil, recent weather conditions, local flooding, ground vegetation, etc.  It's a bush pilot skill based partly on intuition as well as instruction from senior airmen with experience flying in the area.


text:
Why does the spanwise flow along a swept wing not accelerate?
I read this article explaining flow around a fixed-sweep swept wing, and it stated that the spanwise flow component does not accelerate, but the chordwise flow component does. What is so special about spanwise flow that it does not accelerate?

Notice in this illustration the line closest to the upper surface of the wing that depicts chordwise flow.  Chordwise means the airflow is perpendicular to the wing whereby it encounters the airfoil shape.  The curvature of the airfoil forces the air to change direction thereby accelerating it.
Spanwise airflow is parallel to the wing, and does not cross the curvature of the airfoil.  This is like travelling along the side of a hill.  Spanwise flow is not curved and therefore it is not accelerated.
Spanwise flow is associated most with swept wings or when yawing straight wings.
Whenever a mass is made to change direction, it is being accelerated:
 December 14, 2007, (Submitted as coursework for Physics 210, Stanford University, Fall 2007)

I don't agree with the high pressure region in the top right corner of your image. Further away from the airfoil the pressure quickly reduces to ambient pressure. See for example this image for a comparison.

@ROIMaison  Good catch.  Image is edited to your point.

In chordwise direction there is a curvature that accelerates the flow. In spanwise direction there is no such curvature.
See this answer for a more elaborate description of the lift generation.


text:
What is the minimum separation between two A380's while taxing in-line?
If you are tailing another A380 on the taxiway, how much separation do you need from your nose to the A380 that you are tailing?

I suggest asking a question like, "are there any regulations controlling the distance between aircraft while taxiing?" It would get a clear answer and would probably be more useful to the community than a question specific to one type of aircraft.


text:
How do the actuator loads (e.g. for the ailerons) vary between different flight phases?
Assume the hinge moment is given as
$HM = 0.5\rho v^2*C_{h\delta} \delta*S*c$
$\rho$ = air density
$v$ = air speed
$C_{h\delta}$ = Hinge moment coefficient
$S$ = Control surface area
$c$ = average surface chord
the resulting moments / actuator loads are mainly influenced by the aircraft's altitude (air density $\rho$), speed $v$ and the control surface deflections $\delta$. (AoA is neglected to keep it simple)
Can there be anything said about the actuator loads regarding different mission types or flight phases? E.g. does cruise (high altitude and speeds, small surface defelctions) cause higher actuator loads than approach (low altitude, low speed, larger surface delections).
I was planning to use X-Plane to investigate this, but as far as I know it will only output the rudder's deflections, not the hinge moment itself.
Any ideas about this?

have you tried plugging numbers in the equation and see what happens?

@Frederico, thanks for your comment. Actually i didn't because i do not have any reliable data concerning the rudder deflections ($\delta$). Of course I could generate some data by simulation (X-Plane) - but I'm not sure how realistic this approach will be...

Notice that the the hinge moment is proportional to dynamic pressure  ($\frac12\rho v^2$) and deflection ($\delta$) and so is the aerodynamic force on that control surface.

For a passenger plane or a jet fighter?

For clearification: I'm interested in the actuator loads for an uav, which will be used in different mission scenarios. However, I started to set up a simulation environment via X-Plane to investigate this further. I'll let you guys know what I'll find out once I have some data. Many thanks so far for your comments

Indeed the hinge moment equation is (with index $_s$ for surface)
$$H_s = C_{h_s} \cdot ½  \rho V^2 \cdot  \delta_s \cdot S_s \cdot \bar{c_s}$$
The moment coefficient $C_{h_s}$ depends on aircraft angle of attack, surface deflection (!) and trim tab deflection, as depicted in the figure below (from this answer). It is not a simple constant linear function due to shading of horizontal tail in the flow of other bits of aircraft structure.

So of course, hinge moment calculation depends on aeroplane configuration and geometry. But as @JanHudec mentions in a comment, the two main variables here are dynamic pressure and surface deflection.
Full surface deflection at cruise speed results in the largest hinge moment. It may also result in structural forces higher than the limit design forces, for instance load factors > 2.5g. It would be safest if the actuator force can never exceed the hinge moment required to reach maximum load factor, which would require making plots of (hinge moment for max. load factor) vs. airspeed, at different c.g. at maximum weight.


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Do two airlines have IATA code N8?
Wikipedia lists N8 at the IATA code for National Cargo Airlines (ICAO NCR), a regional airline based in Orlando, Florida. AirlineCodes.info and other sources list N8 as the code for Fika Salaama (ICAO HGK), which is based in Uganda. Both are currently in operation. What on earth is going on here?

IATA issues duplicate airline codes to regional airlines where the codes are not likely to overlap, from Wikipedia:

Controlled duplicates are issued to regional airlines whose destinations are not likely to overlap, so that the same code is shared by two airlines.

This happens because IATA uses a 2-letter code for for airlines which has a limited range of available codes. Since NCA doesn't operate a passenger service in the same region as Fika Salaama, it would be very unlikely to confuse the two.

The question is about a cargo airline. Can it ever occur that one and the same IATA code is given to 2 different passenger airlines (e. g. one small American airline, which flies to 2 and a half cities in the US, and a small Russian airline, which does the same in Russia)? In this case they are not likely to overlap, but if someone uses the IATA code as an airline identificator in a database they are screwed...

@DP_ It would be foolish to use the IATA code as an identifier in a database, since many airlines don't even have one. Wikipedia says nothing about the airlines not carrying passengers and, for example, I9 is used by both IndiGo (a large Indian domestic low-cost carrier with more than 100 A320s in its fleet) and Air Italy (which owns 15 passenger 737s and 767s and now flies under the Meridiana brand).

@DP_ NCA also has a scheduled passenger service.

@DavidRicherby FWIW, according to IATA's own database, I9 is indeed Air Italy, but Indigo is 6E

@Pondlife I see the problem: there are airlines Indigo (lower-case g, in the US and now defunct) and IndiGo (upper-case G, in India). Wikipedia's IATA code page linked small-g-Indigo to Indigo (airline), which redirects to big-G-IndiGo and I'd not noticed the difference. Now fixed.

@DavidRicherby I actually meant that IndiGo (the Indian airline) is 6E. If you look at the IATA DB, it lists 6E as "Interglobe Aviation Ltd. dba Indigo". InterGlobe set up IndiGo, so I'm fairly sure that's the Indian one. In fact, I suspect that Indigo was 6E, closed down, and IATA reassigned the code to IndiGo. I say that because the actual code is 6E*, and Wikipedia says the * indicates a controlled duplicate, following a delisting. Moral of the story: capital letters matter (even IATA has them wrong).

@Pondlife It's all too confusing. But I agree that Indian-IndiGo=6E; an incorrect link on Wikipedia caused me to confuse that with American-Indigo.

@DavidRicherby If I wanted to find out all IATA codes assigned to more than one airline, what's the starting point? Background: I happen to know some organization (regional player), which assumes the uniqueness of IATA codes. I want to find out, how bad the problem can become.

If you check IATA's own code database, N8 is used for only one airline: National Air Cargo Group, Inc., doing business as National Airlines.
The same search tool says that Fika Salaama doesn't have an assigned IATA code. I'm curious how you know that it's in operation; Google can't find any direct information on it, and third-party aviation sites come up with automatically generated pages. As we've seen here before, there's a lot of incorrect - or at least outdated - information out there that doesn't always match what IATA's own database says.


text:
Why flights route is so different?
Let's take a look to itinerary of a flight from Dubai to Tokyo taken here

And from Tokyo to Dubai

It's the same airline.
One more example. Here is the route of flight from Istanbul to Tokyo

And from Tokyo to Istanbul

Can somebody explain why return route is so different flying from East to West?

base guess, it has to do with winds aloft.

Also related: https://aviation.stackexchange.com/questions/13428/ and https://aviation.stackexchange.com/questions/29926/

Also note that the map projection (at least for the last example) makes the difference appear much bigger than it actually is

As @J.Hougaard mentionned, routes are bent by the map projection. Here a view from above the Earth. On this image this is the shortest path (great circle) which is shown. You can change the type of projection on the page, as well as the center of the map. You may also add intermediary waypoints

Why is a question about asian flight routes marked as a duplicate of a question on transatlantic flight routes?

@falstro probably because it's the same reason and we don't need a question for every route possible.

@Notts90 Interesting, do you have any literature reference to back up the claim that it is, in fact, the same reason? If you so, can you put it down as an answer? :) Seriously though, someone might actually disagree with you,  these particular instances could - for example - be geopolitical reasons and not jetstream. Do these routes actually correspond to the jetstream? I've made the same case over and over, the question is not a duplicate. The answer might be, but are you 100% sure it is? If not, someone else might actually have a better answer.

@falstro no I'm not 100% but I also didn't VTC or flag the answer as dupe. I'm just suggesting the probable reason why it was closed. If you have evidence to the contrary then post it in chat and get it reopened.

@Notts90 I see that, I'm just countering that reason for others to see. You just got caught in the crossfire, sorry :)


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What can I do to save my life if oxygen masks fail to drop down? Is it possible?
What is the safest and fastest solution (method) in this situation?

Are you asking in the context of a depressurization event at high altitude?

Punch the guy next to you and grab his. Otherwise you will probably pass out, but it's unlikely you'll die.

Yes I'm asking in the context of a depressurization event at high altitude!

Okay. How about the extra masks that you could grab from the row ahead, the row behind or across the aisle?

Have any commercial airliner passengers ever died of hypoxia due to a depressurization event?

@TannerSwett You may want to open a new question to ask that. But there was one commercial flight that I know of where all the passengers died after a depressurization, although they probably died on impact but were all unconscious, including the pilots.

The best thing you can do is basically nothing other than remain clam and follow crew instructions. As long as the pilots have oxygen, you'll be fine. You might pass out, but you'll regain consciousness once the aircraft has returned to a lower altitude. There are generally no long-term adverse effects. Now, if the pilots pass out, that's more problematic.

I'd be asking yourself if you want to remain conscious....


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i just bought a plane and want to rent it out to a Flight instructor!
So I just bought a plane and have a flight instructor that wants to rent it from me for his some odd 12 students. Now, I already have a DBA for my real estate business, could i have my DBA own it or? I guess what i want to know is what is the best way to go about setting this plane up so that i can, in the future do a FBO that i plan to grow to more than one plane? I need to protect myself now but prepare for more business.

This is called a "lease-back" and it is highly recommended that you talk to an aviation attorney for this. You can end up with a lot of liability and expenses with a poorly written contract. For example, when used for hire, you need 100 hour inspections. With 12 students that could be every 2-4 weeks. Who pays for it? What about when a student bends something up? Who pays your insurance, which will be much higher? Overhauls? Avionics upgrades? Other maintenance?

Here is a great read from AOPA on lease-back

Talk to a lawyer.  You need an airtight lease agreement
Do not tie it to an existing profitable business.  If someone dies in your plane the family will sue everyone in sight and a jury will award them some serious cash.
Get the FBO's insurance to cover you and get a copy of the insurance document to that effect.  Then go out and buy additional insurance.  Not kidding.  Talk to a broker.
Leasebacks are great when stuff goes well but it's still a business and when SHTF it gets downright nasty.  Aviation is a great hobby but it's a dirty business.


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Why are aircraft parts built in different places and assembled in one?
Airbus has its manufacturing facilities in Spain, France, Great Britain and Germany. Each country produces different parts of the aircraft and is finally assembled in one place.
Why is this? Wouldn't it be more economically sound that everything was built and assembled in one place? Is it because all of the countries in Airbus group have to have some work? Is it because you can't get all those workers in just one country? I don't understand economical and logistical logic behind it (if there is one).
I believe Boeing has the same practice which puzzles me even more, since USA is more of a one country than EU. Is it really cheaper to manufacture something big as a wing overseas and transport it to one facility?

I am not sure you can get a really qualified answer—someone from rather high up in those companies would have to confirm it—or much detail—the topic would probably fill a book.

One big happy continent.

Planes from Australia or Antarctica?

This really isn't an aviation question, since many things, from cars to computers, are built from components made in different locations and shipped to another place for final assembly.  The reasons have nothing whatsoever to do with aviation.  Might be answerable on the Economics site?

Italy imports a lot of grain, makes pasta and exports it, often to the same countries where the grain came from. Wouldn't it be easier for them to make their own pasta? The answer is that the cost of outsourcing manufacturing is often lower than building factories, hiring people, training them, and so on.

Actually you CAN answer that. And all anwers here are wrong.

A factor not mentioned in any answers but I don't think is worth adding an answer just for this is that while parts manufactured elsewhere do need to be shipped to the assembly point if you manufactured them in the same place you'd still need to transport the raw materials to that point so you may not be making any savings if the manufacturing plant is nearer the raw materials (whether this be where they are mined, etc or a convenient import location). Basically you will be paying to get things from A to B whether it is in raw form or assembled form which allows other factors to come into play

...because you can't assemble a plane without bringing all the pieces together?

See https://en.wikisource.org/wiki/The_Wealth_of_Nations. Quick summary of Chapter 1: in a winning track and field athletics team, it's fine to have one guy who can run 100m in 10sec but only high-jump 4 feet, and another guy who can high-jump 7 feet but only run 100m in 15 sec.

"Why is this? Wouldn't it be more economically sound that everything was built and assembled in one place?" If you'd build the same type of plane for 25 years and just that type of plane, probably. Building multiple planes which get more complex in varying amounts of time? No way. Too complicated to keep your building and personnel properly organized.

So, @TomTom, care to enlighten us further? Simply stating "all the answers are wrong" doesn't really help the situation.

Well, it is a political decision based on the investments into the company which actually did a have a lot of goverment funding - from guess which countries.

One point in particular is politics. Especially with Boeing, which is subsidized by the government, not least of which is tax cuts. One way to ensure support from congress is to have a stake in many states. Any Congressman that opposes them they can threaten to leave and blame the "terrible" Congressman.
With Airbus is similar but with countries government instead of congressmen.

Also generally, read up on Comparative advantage

You can only hire so many people at one place, and also only find so much land there, so when the whole process no longer fits, there is no other option than start building components at other places and move them to the final assembly place.
In part, it is also historical. Airbus, but to an extent Boeing too, was formed by mergers of smaller companies as building a plane became more complex over time. So the companies got already working facilities with already qualified workers. Closing them down would lose them those workers, and cause quite a bit of bad publicity too (and at least in case of Airbus some political pressure), so they got used for whatever part of the process fits in them.
And some factories simply don't have any unused land around them, so the companies can't grow them even if they want to and have to open new ones instead. This is probably worse in Europe, which is more densely populated, so building a really big factory is basically out of question anywhere.

But why different countries instead of, e.g., cities?

@SalmanA - because different cities can easily be in different countries. Or, for Boeing, in different US states.

@SalmanA, the argument about so many people and so much land applies to larger areas too. When you have several large factories already in some country, hiring qualified people becomes harder as you've depleted the pool of those qualified and interested from wider around and you have to expand somewhere further away. Also, sometimes it is just cities—Airbus has factories e.g. in Bremen and Hamburg, which are quite close together, but neither factory has any unused land around it to grow on, so they can't expand them even though they'd like to.

There are many considerations in where parts are manufactured or assembled, and not all are directly related to economics.
Both Boeing and Airbus have assembly lines located around the world, so it can make more sense to consolidate production of components in one place. Manufacturing large parts requires a huge investment in tooling and machinery. For example, the large autoclaves used to produce large sections of the 787 were very expensive. Boeing decided to locate them all in South Carolina, and fly some of the parts to Washington for final assembly. Even with modern technology, producing repeatable parts is much easier with one location. Some skills may also be fairly specific, and build up the expertise in a certain area.
There are also political aspects. In return for allowing their airlines to purchase aircraft, countries like to see some sort of return on that investment. You can imagine there might be a bit of backlash in Europe if Airbus decided it was going to move all manufacturing to France. There are already concerns over how Brexit may affect Airbus manufacturing in the UK.
So why not just have all the final assembly in one location as well? Politics factor in here too, which is why Airbus-designed airliners being assembled in France, Germany, China, and the US, rather than in one location. Even Boeing, which had traditionally assembled all of its aircraft in the Seattle area, chose to locate major parts of 787 manufacturing and assembly in South Carolina, and recently opened a finishing center for the 737 in China.
But the deal goes both ways. Some of the cost of splitting up manufacturing locations can be recovered by "shopping around" between cities, states, and countries, to see who is willing to offer more compelling terms in return for moving jobs there.
There are also economic reasons to split up production. Natural or manmade disasters, politics, or just accidents can affect local areas. This allows companies to diversify their investments geographically, so that any issues may only affect a small part of the supply chain, rather than most or all of it, if it were concentrated in one place.

Another political factor: US defense contractors are notorious for sourcing parts from every Congressional district in every new plane because nobody wants to be caught voting against jobs in their own district.

I think the political aspect is the main factor here. You can't think of Airbus and Boeing as simple privately-owned companies. At least for Airbus, it is largely owned by different European countries, which will ensure some of the jobs will be spread around.

@StephenS it's more often a requirement by congress for them to do so or they won't get the contract. This was notoriously the case with the Space Shuttle and other major systems designed by government agencies for construction by private industry.

@jwenting That's another way of saying the same thing, if you think about it.

Unions are an issue with Boeing, having poor relations and a number of strikes in the past. Washington State has relatively strong union laws and South Carolina does not ("right-to-work" state), plus the South has not been strong on unions in general. Foreign car makers have had the same considerations too.

"Both Boeing and Airbus have assembly lines located around the world" Airbus certainly does, but I thought all of Boeing's final assembly lines were in the U.S.? For the commercial airplane division, there's only Renton, Everett, and Charleston, right? (And Renton and Everett are both suburbs of Seattle, just 30 miles from each other.)

South Carolina is also very heavy on both hydro and nuke power, which makes power rather cheap outside peak air conditioning times.   Easiest way to heat an autoclave is electric.

@Harper That's one factor, but only the rear part of the 787 fuselage is made in SC. The rest of the major structure comes from suppliers Kansas, Italy, and Japan, the latter of which don't have cheap power.

There are several reasons like

Risk reduction by second sourcing. This means that a manufacturer tries to sign up several manufacturers for the same part to make sure, that if one can't deliver by whatever reason, there will be a backup.
Having multiple suppliers enables competition between them, eventually lowering the price
Production for some parts may be better concentrated around the part than the final product. Think engines, where it's more useful to produce them in their own plant then have an engine fabrication for each and every plane type - despite the fact that engines are custom to each.
Production requires according production technology, so it might be useful to have parts made by specialised partners than building a line on site. Like let someone with facilities and knowledge of carbon production do whole wings on their own instead of setting up a new plant to do so.
Especially with airliners parts can be so large, that they require a seperate plant which in turn can be locates anywhere - the wing production for Airbus in the UK is agood example here.
Last but not least is size of a plant. It may be hard to get enough workers and even less specialist concentrated all in one location. Detroit is a great example how this may result in hard to handle giants.

Well, and then there is history. Usually large manufacturers have been grown by mergers and acquisitions of several companies with existing sites of their own. Continuing full scale production on all sites doesn't make much sense, closing them down may result in losses - not just monetary but more important it may result in a hefty loss in qualified workers and engineers. Modularisation and specialisation of each site may turn this into a win-win.
Unless what's often perceived, history is no reasoning on the long run, as plants may be moved or closed at some time. Within Airbus there are internal competition processes between all plants when it comes to new products or production lines, when it's about to figure out who is getting the job.
Thenks to Brexit reporting the crancshaft of the BMW Mini is a great example that even a brand new production, setup with only little previous history to obey, will result in production cycles where parts get moved several times around the world before the final product is done.
It gets cast in France, forged and machined in England, build into an Engine in Germany (or Austria), which in turn gets moved to the UK (or Netherlands where the second Mini plant is) and finally put into the car.
That's the way modern (complex) products are made and airliners are no difference.

Having multiple suppliers so they will compete among themselves (and also provide redundancy) is smart.

@zundi Of course the flip side of that is you're competing to pay the most so that your parts get made instead of someone else's :)

This has not mich to do with aviation. All big companies are required to spread around the world. It depends on where your workforce lifes, where does the customers reside and where you get your natural resources and political conditions.
Airbus was merged together from smaller and bigger companies founded across Europe. It was fostered by politicians* across Europe and because some companies have special abilities, workers, tools and so on they produce their special stuff and others put it together. Airbus also has bought some things, e.g. the A220 project from Bombardier.
Boeing has bought a lot of companies, just to name McDonnellDouglas or Rockwell or Hughes. And also facilities across the world, e.g. even China.
The main point is, neither a large microsystem nor a big monolith are perfect. The nature of infrastructure, people, place, history and logistics prefer a mixed setup. Also outsourcing (expensive and risky) nor insourcing (expensive and risky) everything are working well.
Some things can get really big, like Volkswagen in Wolfsburg, but it requires even own power plants. But well, they produce cars in Czech, Spain, Italy, China and the USA. Probably forgot something, Great Britain? Mexico? South Africa? Brazil? So it’s rather distribute. Intel is another example, their Fabs are big and spread around the world. Same for software, Red Hat is mainly working in Czech and the USA, but also in some other places.

AFAIK the famous/infamous Franz Josef Strauss was a supporter of the A300 and himself pilot.

But FJS did not start or land the plane himself. But for press photos he took the pilot seat.

@Uwe. Hehe! He had his hour with the ridiculous flight from Bavaria to Moscow in 1988. They survived ;)

The laconic answer is for political reasons. You partition the job to many areas, so that everyone gets its workshare, and keep their economy moving.
Pros: A site capable of building every single part of an airplane needs to be colossal. By scattering the work, you avoid that.
Cons: Merging all the parts is prone to errors, and many airplanes were delayed because different areas were using different software versions, metric units, etc.
Examples: A380 late delivery due to crossed wires, where "The wiring wasn't following the expected routing through the fuselage, so when we got to the end they weren't long enough to meet up with the connectors on the next section", and then basically restarted from scratch, and did that manually.
Boeing 787 subcontractors unsynchronization, where it also led to major delays.

THIS is the correct answer, particularly with Airbus being a "European" company. Having major presences in the major european states is sort of a condition for getting the EU money to start this.

As someone who works for Airbus...
Airbus now is the conglomeration of many old companies - as recently as 2014 there was a merger bringing in EADS Astrium satellites, Paradigm security, Eurocopter, Safran launcher services etc. into Airbus GROUP. Not all of these are related to the building of planes, but they all had their distinct fields of work prior to being merged.
Specialisations for designing certain parts of a plane/spacecraft are kept locally. The team specialised in optimising engine performance doesn't need to know about the avionics system, the team in charge of landing gear doesn't give a Gnats knee what the windshield looks like.
What determines the specialisation where, in this case, is in some ways related to the previous specialism of the absorbed company/site. I don't know a great deal about the Airbus aircrafts business history, so I'll digress from planes into an area i'm more familiar with.
Airbus Portsmouth used to be an EADS Astrium site, before that it was Matra Marconi, before that Marconi Electronic Systems... who produced electronic components for space purposes.
Nowadays, in PTH we make payloads for satellites that get fitted to the "bus" built in Stevenage, that gets coupled to the transfer module, solar arrays, antennas in Toulouse, and finally shipped to launch from a few places around the globe. This was the case when we were Astrium, and stays the case now.
You've also got to think about the sheer size of the things. You need a vast amount of space to put a wing together and test it - it's just not feasible to move all the infrastructure, and people, to a single location. You'd need to build a small town around it to accommodate all the employees - And then convince them all to up sticks and move to the new site.
In terms of manufacturing wing-size things in one place and transporting them to another country.... I give you the Beluga, Specifically modified to do exactly that.

I know the Beluga is real, but it still looks like someone's poorly Photoshopped attempt at a joke. And this one, with the "1" on its forehead, looks like it bumped its head on the door as it was coming into the hanger and got some paint on it.

TAX and Financial reasons
Imagine a location really needs employers, to provide jobs.  So the local or national government may choose to subsidise part of the costs.
Example - Tesla Gigafactory-1 was sited in Nevada, whose offer:

included $195 million in transferable tax credits...

from https://en.wikipedia.org/wiki/Gigafactory_1#Factory_location

Sorry, its not an aeroplane, but its a clear example of a sub-component factory being located at least in part for financial reasons.

But it can nearly fly. It just needs a bit more work on the autopilot landing algorithms. https://www.youtube.com/watch?v=2xFji9-xgMw

Nevada has huge swaths of desert where you can build a gigafactory—and you'll still face the problem of persuading people to either accept the long commutes, or move somewhere closer where the coyotes bid good night. Europe does not have any such large undeveloped areas, and has enough work opportunities closer to a nice city that nobody is going to follow a company to the middle of nowhere.

The main reason is the manufacturers have mostly gone to a "risk sharing partner" model of development because no one wants to put out the coin required to develop an entire program in-house.  So manufacturer X will take on company Y, Z and D and C as partners, more or less co-equal, to design some of the major components as well as manufacture them.  The partner takes on the costs, support obligations and profit share of the component or system.
The upside is the OEM can develop a design with only half the capital of doing it in-house, and only takes half the risk, but at the same time gives up half the profit potential and gives up a lot of control because the partner is "at the same level" you might say and is not as easy to boss around when things aren't going well and there is disagreement on what to do about it.
Not ideal, but better than a project not going forward at all.

In the case of Airbus the case is quite political. Several European countries merged (some parts) of their defense industry. Reasons may be
political control over high tech Remember the EU started as a project to give control of steel and coal, indispensable for large scale military production, over a supranational community. That was partially because after WW2 the other European states wanted to watch over the military buildup of the Germans. Why not do that with the High-Tech conglomerate? Also Airbus, as agreed between France and Germany, had for a long time always a double CEO, always one German and one French. Interestingly the large nations, except Germany, kept some company in house (BAE, Dassault).Nobody can see into the future and every state wants to be independent from external defense industries, in case the foreign suppliers experience "mysterious delivery issues" after a political fall-out. So it is better to have able defense suppliers in the country.
high tech Why having a large (I don't know how many, but I guess something in the 10-20) number of small companies build up the necessary high tech when one giant could do better?
So, in case of Airbus:
The EU doesn't care about inefficiencies at Airbus as long as they get things more or less done. The reassurance to all members that they can have military equipment (and keep a watch on the larger countries defense procurements) is much more important. Should one day a larger part of all those factories and Know-How be located in, say Germany, some people would become very nervous.
Wait: What about the civilian range of Airbus?
I suppose that is just to keep foreign competitors from having a monopole. Also some cash flow won't hurt


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Flex temperature isn't actually "fooling" the FADEC, right?
I'll be using Airbus terminology here because that's what I know, but I guess the concepts are universally applicable.
The way I understand flex temperature is: It's a user interface for pilots to request a derating of engine power to reduce wear on the engine. Simple enough, makes sense.
But in understanding why this is being input as a temperature, I have often encountered confusing explanations. Many videos and forum posts will say something like this:

Flex temp will fool the FADEC to think the outside air is hotter than it actually is.

That cannot be correct, right? If the FADEC actually thought the air was less dense, then if anything it would increase engine power, not derate it.
What makes more sense to me is this:

By entering flex temp, you're intructing the FADEC to produce only as much thrust as TOGA would produce at that increased temperature.

Simple. We're not fooling the FADEC, it knows full well how much thrust it is producing and that's good.
Using a temperature value as the input (instead of some percentage of engine power) also makes sense because pilots need to be aware of this parameter anyway when considering altitude, runway length, and aircraft weigth to verify a takeoff is possible.
If I'm correct, why is this "myth" of fooling the FADEC so prevalent? I find this notion very confusing and counter-productive when learning about this.
Does the FADEC even actually deal with outside air temperature in its logic? Why and how? Or does flex temp really just translate to a thrust value (possibly together with altitude)?

M'not an expert but what about the fact that a higher outside temperature would result in higher compressor outlet temperature, and thus higher turbiine inlet temperature?

@Abdullah You're saying the FADEC will measure thrust by looking at EGT? Hm, I don't know. It would be interesting to learn how the FADEC can measure actual thrust. Can it even?

The engine must not be allowed to overheat, that's what I'm saying. A higher simulated outside temp = higher simulated turbine inlet temp, right? then we have to throttle back

There are at least two misconceptions in your question:

The way I understand flex temperature is: It's a user interface for pilots to request a derating of engine power to reduce wear on the engine.

This is not quite correct. A derating would imply that the engine thrust needs to remain at the derated level after an engine failure. A FLEX or assumed temperature method takeoff allows setting higher thrust in case of an engine failure, so it's not a derating. See also What is the difference between Assumed Temperature and Derate takeoff thrust?

If the FADEC actually thought the air was less dense, then if anything it would increase engine power, not derate it.

This is not correct when the engine is temperature limited. The hotter the air, the hotter the EGT at the same fuel flow. Therefore, the FADEC has to reduce fuel flow to the engine for higher air temperatures, which reduces thrust.

Consider the following slide from this Airbus presentation:

You can see that the engine is flat rated (see What is a flat rated engine?) below a temperature Tref, which means the engine is not limited by EGT and can provide the same thrust regardless of temperature (see e.g. this answer for other limitations). If the temperature is higher than Tref, the FADEC has to reduce fuel flow to keep the EGT below the limit. This results in less maximum available thrust.
By entering a FLEX temperature, the FADEC will reduce fuel flow to the engine as if the actual temperature would be that high. We can argue about the semantics of whether or not this is actually fooling the FADEC, but the fact is that the FADEC will reduce the fuel flow accordingly. This will then actually give you a lower EGT than the maximum because the actual air temperature is colder and therefore reduces engine wear and tear.
The FCOM contains some additional information about what the FADEC does:

The FADEC system performs the following functions:
Control of gas generator

control of fuel flow
acceleration and deceleration schedules
variable bleed valve and variable stator vane schedules
control of turbine clearance
idle setting

[...]
Power management

automatic control of engine thrust rating
computation of thrust parameter limits
[...]

(Airbus A320 FCOM - Power Plant - FADEC)

When the thrust lever is in the FLX/MCT detent:

On the ground
The engine runs at the flex takeoff thrust rating if the crew has selected a flex takeoff temperature on the MCDU that is higher than the current Total Air Temperature (TAT). Otherwise the engine produces Maximum Continuous Thrust (MCT).

(Airbus A320 FCOM - Power Plant - Thrust Control System)

Thank you! I was unaware that an EGT limit is what causes the thrust reduction, not just the physical effects from the reduced air density.

There are other limits to engine operation as well as thrust and EGT temperature, for example maximum rotor speeds.
Thrust is often limited in "hot and high" situations because the LP rotor can't run fast enough to push enough air through the engine to deliver maximum thrust. So "telling the FADEC the air is less dense than it really is" is likely to produce less thrust, not more, which is the desired result.
I agree that "fooling the FADEC" is not a very precise explanation for what is going on, but it makes a sense to give the pilot a control input that is easy to understand, such as "fictitious outside air temperature".


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What are the 2 protrusions next to the fore ground lights on the Tu-22M3?
Here's a reference image :

What are those 2 spokes coming out next to the ground lights ?

They appear to be pitot tubes, part of the air data system.


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What are these spinning discs next to the throttle of the Boeing P-8 Poseidon?

The source video can be found here and the GIF is from 0:21 onwards.
What are those 2 spinning things next to the throttle ?

Related: Why are the 737 trim wheels located so close to the seats?

Those spinning discs on either side of the throttle quadrant are the stabilizer (stab) trim wheels.
The stab trim system can be actuated by electric trim switches on either the left or right control yoke, the autopilot (AP), or by manually turning the stab trim wheels. The yoke mounted electric trim switches "spin" the trim wheels at the high speed seen in the GIF above, while the AP turns the wheels at a relatively slower rate. A stowable handle in the trim wheel can be pulled out to allow for faster manual turning.
I've heard that this handle can be very painful to the knees if left unstowed and either the AP or especially the electric trim turns the wheels.
See "Why I hate the Boeing 737" for more info on the system, including photos of the trim wheel and stowable handle:


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What factors come into play when reducing the total noise generated by a helicopter?
I simply cannot understand how a helicopter can be made quieter. What are the things that would considerably affect the noise signature of a helicopter ?

Possible duplicate of What do we hear, on the ground, from a helicopter in flight?


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Have there been any 'proper' field trials of Automated Air Traffic Control?
Have there been any 'proper' field trials of Automated Air Traffic Control?
Specifically, something that has been tested on larger aircraft and has come beyond the drawing board. By automated I'm implying that all decisions on movements are made by computers and instructions would be for instance transmitted digitally to the cockpit.

There's a book, whose name I've forgotten, by Arthur Clarke about the British efforts during WWII to develop safer landing systems. For one, they used radar to track an incoming plane, and the ground controller told the pilot what to do. On an early test it worked fine, until the plane headed off in the wrong direction and didn't respond to new instructions. Turned out they were tracking the wrong plane, which just happened to be doing roughly what they were looking for. The actual plane was out over the ocean, and the pilot was getting nervous about instructions that didn't make any sense.

I suspect that this will really start to happen as a 'side effect' of integrating drones (UAS) into the air traffic system. The current ATC approach won't work for unmanned systems, and as drones become more numerous, autonomous and fly at higher levels some kind of automated control will be needed. It may still take decades, but it's hard to see it not happening eventually.

even drones are remotely controlled by a human operator for takeoff and landing, whether or not the launch/landing sequences are automated in software.  the operator still has to get proper tower clearances.

@PeteBecker: That specific method is called PAR.

There have been many trials involving large aircraft and various levels of ATC automation. However these trials do never involve more than a handful of aircraft. And always with a human Air Traffic Controller tightly in the loop for safety reasons.
And never were all decisions made by the automation system. Progress comes in small steps.

Examples/references?

No
Short answer, but there has never been anything resembling a "proper" trial. There have been a few small scale, limited and tightly controlled trials, but nothing over any significant time frame, involving a significant number of aircraft, or even involving aircraft in "normal" use.

I suspect one of the bigger issues with automated ATC is you will always need human controllers to be there to take over when the automated system fails.
Moreover, since the job of an ATC controller is a difficult one that requires a great deal of mental dexterity to translate a two dimensional display or moving object information into a mental picture of a three dimensional airspace, the individual really needs to be active regularly enough to keep those skills sharp.
There is no doubt a computer can monitor and extrapolate how traffic is moving relative to one another far better than a human can, but the whole communication with a human thing is another story. It might work great as long as everything was operating routinely, but odd things happen quickly.
As such, you sort of want it automated but at the same time... you don't.
I rather suspect, and hope, that instead of going down some fully-automated route, the tools presented to the human ATC will improve instead.
How that blends into moves to use pilotless aircraft.. I have no idea.

Much the same way most air transport category aircraft can land themselves via auto-pilot, but the pilots don't just sit back and read the paper while the plane does all the work. Eventually, the computers will fail and when that happens the pilots need to be in practice for when they do. Therefore, the pilots fly most landings themselves.


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How much does a Black Box Underwater Locator Beacon (ULB) cost?
I'm curious if anybody can provide a rough price estimate for a commercial aviation ULB like those used on Black Boxes.
Area of interest: Europe i.e. Euros, EASA CS-25.
(For instance the RJI ULB-362 or the Dukane DK-120, but any equivalent is good)

There is one listed here on Ebay for $750. Some of the makers like L-3 list contact info for getting pricing, all of the other sales sites I am finding look like you need to submit for a price quote.


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Triple engine failure; which would you choose to keep left?
It is well known that planes with two engines must be able to land with one engine inoperable for their certification, and that four engine planes with two inoperable.
Now, suppose you had a four engine plane with 3 engines inoperable, and only one remaining. In terms of the greatest likelihood of survivability of this incident, is it at all favourable to have the engine closest to the body of the plane active, or the one further out?
As far as I can see it, there are two main ways to tackle this; one is by looking at incidents where triple engine failure occurred (which is very rare) and seeing whether it makes a difference.
The other approach is how does it affect the controllability and maneuverability of the aircraft theoretically or based on testing depending on if one has the jet engine closest to the body active, or the one further out on the wing. It may be that the difference is negligible, but I'd be curious if there can be some argument made to favour one option.
There would be other variables to take into account, so to narrow it down a little more, I am considering only jet engines, on aircrafts used for commercial flight.

The yawing moment will be higher if the outboard engine is operating, but during certification, flight is demonstrated with both engines on one side failed (therefore both engines on one side working) which would be an even higher yawing moment than the single engine working.  My short, intuitive reasoning (not really an answer) would be that it shouldn't make a difference if you have a well-trained crew who doesn't let the yaw get away from them.

@Lnafziger Thank you for introducing me to the terminology too ('outboard engine') - I was sure there had to be a word for it! :)

Like lnafziger said, the outboard engine has a longer yawing moment. So if you had your choice you would choose an inboard one

It's a minor point, but one of the rules is to avoid turning into a dead engine. Thus, assuming the captain will be flying the aircraft in such a situation, I would choose to have the inboard engine on the left side running. That way in maneuvering for a landing I would have the better visibility on my side in the direction of the turn while avoiding turning into the dead engines side.

@Terry These are all good responses and sufficient to be answers.

@mins That is how I intended to phrase it - as if hypothetically one had a choice.

Using the inner engines allows you to maneuver easier as the yaw moment is smaller in comparison to the outboard engine which also means you need less rudder inputs to keep the course. The big advantage of needing less rudder to keep a straight path of flight is that you can react better because the rudder can move a bit more.
Which sides engine to use is depending on the wind situation (I would use the engine on the side the wind is coming from as you can turn into the wind better to keep your course) and other influences like if you need to turn left or right more often; avoid turning into a dead engine as Terry already mentioned).


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Could this propeller work on a quadcopter and decrease the sound?
I came across a video yesterday that showcased a propeller design that looked very interesting. I am a regular drone flyer and I constantly look for exciting things to try out. Would this design in theory work and if so, would the sound of the propeller decrease by a lot? I was planning to 3d print them out and test them but i wanted to share the video with more experienced people first to see if i would waste my time or not/hurt the engines by using them.
Video
My idea is to put it on my quadcopter that has 2300kv motors and works well with 5" props.

I love the description of the video on Youtube: free green first ever world novelty perpetual best new car vehicles drone понтонни ВЕЦ

Wow, a triplane propeller. Well, the propeller would kind of work, but not as well as a regular one.

2300kv? As in kilovolts? Er...

Sound might decrease as much as the design lets you run the propeller at lower RPM for the desired loading. The efficiency is going to be definitely worse though.


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Are modern aircraft (fully loaded and fueled) able to operate from hot and high airports?
Some decades ago, aircraft had really difficulties to take off and land at high altitude airports in hot weather.
I'm not sure whether advanced FADEC and better mastering of aerodynamics might today allow a heavily loaded and fully fueled FedEx MD11 to take off from 5000+ feet elevation airport in hot weather.
I'm curious to know about how much progress there was over the last 20 years or so.

I really can't work out what you're asking. I started to write a comment about how your question is based on a false premise but I realised I can't actually figure out what your premise or your question is. What do you mean by "a real improvement in these 'worst-of-ll' kind of scenarios"? (What does the thing in quotes even say?) Is your question, essentially, "Are modern aircraft designs better able to deal with hot and high conditions than older aircraft were?"

It might also help to explain how you expect a fancy FADEC to help the fact that you're sucking a smaller mass of air into the engine and that the wings are acting on a lower mass of air (because heat and altitude both mean lower pressure, which means less air per given volume).

The edit was a good attempt at clarifying the question, but I don't think it's what the asker intended. The MD-11 first flew in 1990, so it doesn't have the modern aerodynamics or control systems that the asker seemed to want to compare with equivalents from the last 20 years or so.

The FADEC may simplify the process of performing a derated takeoff but it can't change the laws of physics. High and hot means you need more runway and when you run out, you need to reduce weight if you want to take off safely.  There's reason why KDEN  has a 16000 foot runway.

"High and hot" covers a wide range of conditions.  In addition, total takeoff distances are subject to a number of factors including, but not limited to takeoff weight, field elevation, type and condition of runway, surface winds, obstacle clearance, etc.
So an MD-11 with a low payload and a meaningful headwind can depart the same airport successfully that could not be done if it were loaded at or near MTOW with a tailwind.  You will have to be a little more specific.

This is a comment asking for the question to be clarified, not an answer.


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Will depression from 20 years ago prevent me from being an airline pilot?
I was diagnosed with clinical depression at age 16 and was on prozac for a year.  During that time I coped and after six months I tried taking myself off the medication because I did not like the feeling of being medicated.  I have been free of this for nearly 20 years.  I have had no relapses, I have never been medicated since then.  I also attribute my falling into it in the first place due to lack of coping skills since I was so young, given my life experiences since then I don't know how I let myself "slip".  However, will this prevent me from ever becoming an airline pilot?  I have saved up the money to go....  Even if I get evaluated and given a clean bill of health does this doom me to be forever be thrown on the "reject" pile???

I don't want any words of encouragement or optimism.... I really want to hear what I'm up against and if its time for me make different life plans.....

What jurisdiction?

Please see answers to this question. A flight surgeon will have the definitive answer for you; at the level of an 'internet message board answer', it's entirely possible the answer will be 'yes' you can fly.

I've read a lot about this. I can't find it at the moment, but an FAA guide for AME's  and anti-depressants lays it out for them. If you a) took the medicine for less than 3 years, b) did not take any other psychotropic medicine in combination with it, and c) have been off the medicine and stable for at least 6 months then the AME can certify you. If you took it for more than 3 years, even if you are off of it now the AME must defer you for a special issuance. If it hasn't been 6 months you have to wait it out and if you are stable off meds the AME can certify you.

The way the guide is written implies that if you EVER took another psychotropic med in combination with an antidepressant then you can NEVER be certified, even with a special issuance. I don't know how flexible they are with those rules, though, because that sounds unreasonable to me and that's where I'm stuck at. But it sounds like you fit a) b) and c), so should have no problem. Only an AME can tell you for certain, though

It does not sound like a dealbreaker, however I'm not an aviation medical examiner. I do not think that depression diagnosed when you were a minor would prevent you from becoming a commercial pilot now, I do not even know if you would be required to declare it to an airline on an application. The biggest hurdle you would have is the medical I would expect. You might need to have a psychiatric evaluation, or it might be far back enough that isn't necessary. It likely depends on the severity of the depression you were diagnosed with on the DSM (diagnostic and statistical model of mental disorders, a tool used by professionals to assess and diagnose mental conditions) scale.
My recommendation would be to talk to an aviation medical examiner. Many pilots deal with, or have dealt with depression, sometimes severe, so it should not be hard to answer. You lose nothing by trying.


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What is the optimum separation between contra-rotating propellers?
What is the optimum separation between contra-rotating propellers?
What factors determine the distance between the two sets of propellers?

On the design you referred (in your original post), note the power is transmitted from the two blade shafts to the single shaft using a push-pull mechanism, this wouldn't work in the other direction, for an engine. The mechanism used is not reversible. This is similar for the second design (valves control), again the power is in the central shaft moving the corrugated discs. That said I believe you're asking about coaxial propellers, which is not clear in the current version of your question. +1 anyway.

When on different aircraft, a few miles will usually do.

Here is a paper that partially addresses your question; however, they discuss a ducted-propeller system.

The effect of axial gaps showed that at the design speed combination best performance was observed at an axial gap of 50% of the 1st [fan's] chord.

A lot of research on contra-rotating props has been done for ships, it seems. This thesis indicates that, for ships,

the effects of the spacing between the propellers is almost negligible with respect to the CRP efficiency.

This paper has an extensive review of rotor spacing for helicopters (it's also a good read for answering your second question). The author notes for one configuration that

the effect of separation distance on the optimal performance of the system is not very noticeable for practical operation,

but for another that

the separation distance significantly reduced the influence of the mutually induced velocities.

What all this tells me is that the optimum separation distance is likely highly dependent on the specifics of the propeller design and the aircraft's overall design. Various airflows from the aircraft structures (fuselage, wings, etc.) would affect the interference between propellors. The propellors' rotation speed, size, number of blades, and chord would all come into play. Furthermore, "optimum" could be a balance of any number of things, but most likely efficiency, thrust, and noise. Any commercial or military design would need to undergo extensive trade studies and CFD and wind-tunnel testing for the specific model, not rely on a general rule.


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Why a parachute for aerobatics only when carrying a passenger?
Per FAR 91.307:

Unless each occupant of the aircraft is wearing an approved
  parachute, no pilot of a civil aircraft carrying any person (other
  than a crewmember) may execute any intentional maneuver that
  exceeds...

So if I'm flying aerobatics solo, I'm not required to have a parachute. But if I have a passenger, both are required to have one.
What is the rationale for that?
I suppose that in something like a Super Decathlon, where the pilot must exit the plane before the passenger, it would be senseless to have one for the passenger but not the pilot. But is there anything more to this?

As a side note, this is once area where European legislation diverge from that of FAA. Parachutes are not required for aerobatics (but typically used as seats are designed for them).

A basic principle of FAA regulations is that you are allowed to risk your own life, but not the lives of others.

Well, as with many issues involving the FAA, the "why" is a bit of a mystery.  Perhaps they thought that the pilot can "lead by example" if a bail-out is needed.  I'd imagine that a lot of passengers would be a little reluctant to jump out of an airplane, but once they see the pilot go I can see them becoming highly motivated!
As far as not needing the parachute if only crew members are on board, the FAA has long held the view that they aren't protecting pilots from doing stupid things to themselves since they are knowledgeable and informed, but their regulations are to protect the "general public", or the passengers in this case, who don't know any better.

"FAA has long held the view that they aren't protecting pilots from doing stupid things to themselves", well said, I like that :)

Except that the bureaucrats disallow you from doing aerobatics below 1,500 feet, even if you're in the middle of the desert or over a remote forest, and by yourself in the plane.

The rules come from a basis at the FAA that a serious accident is one with multiple fatalities, not just one.
From AC-1309:
Catastrophic: Failure conditions that are expected to result in multiple fatalities of the occupants...
Aircraft that have only one seat do not need to be designed / certified as stringently as aircraft with 2+ seats. Along with that, if only one person is in the plane, you can't have multiple fatalities, so there's no such thing as a catastrophic risk.


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Is there any limit to how many times an aircraft evacuation slide may be deployed?
I've seen multiple videos online of evacuation slide tests and they all tend to be almost violent as they are very fast and loud, but I can't help thinking that it must put a lot of force on those seams when they inflate and along with that the material. Is there any limit to how many times these may be deployed before they must be retired?

must be Overhauled Every 3 Years to be Airworthy.

The slide has to be removed from the aircraft completely (generally) and sent back to it's manufacturer to be inspected and repacked, but yes, it can be reused.
This article talks about it in more detail.
As a far as "how many times", I would assume until it breaks ;).  Though honestly, I doubt a slide would ever be deployed more than once, maybe twice in it's life span.

How about if it has been used as a liferaft (exposed to salt water, etc.)? If the plane itself is a writeoff, would a reconditioned/repacked slide be accepted by the FAA, etc. for use in a new plane? Could there be hidden damage from heat (fire) that they wouldn't want to risk that? If a slide is usable as a raft, I would imagine they could remove the emergency beacon and sell it for whitewater rafting use!

If it doesn't pass inspection then it isn't reused (yeah, kind of a vague response, I know.  But they don't really talk about their inspection criteria in anything I read.)  It would be interesting if they sold them for different purposes though, that could be an interesting rafting experience!

@phil: do whitewater rafters commonly use defective substandard equipment designed for other purposes and rejected as unfit for use?

@RedGrittyBrick: Commonly?  Nope.  But I've met plenty of uncommon folks that  are willing to try just about anything once ;).  The real question is if any company that makes them would be willing to put up with the liability...  My guess is no.


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Is it possible to bluff one's way to the flightdeck like in Catch Me If You Can?
I was watching some clips from Catch Me If You Can starring Leonardo DeCaprio as Frank Abagnale.
I was wondering- If brought a ticket on an airline today, came dressed up like a pilot, would you, be able to sit in the cockpit? (assuming pilots are normally allowed to jumpseat in that jurisdiction) Say you come onboard the plane and present them a fake ID at the door. Is there anything to prevent this from happening, or are we still as vulnerable to this type of trick like in the movie?

You wont be able to bluff your way in, but before i can elaborate I need to verify it isn't SSI. You need specific authorization to occupy a flight deck jumpseat.

@casey curious because of this incident: http://edition.cnn.com/2013/03/22/travel/pennsylvania-pilot-impersonation/

In my opinion, in the period before I retired in 1999, it would have been easily done. One problem, though, would have been to make sure they didn't use a name that was on a scab list if approaching a captain that was a dedicated union member.
I have no idea what the situation is now, but I'd be very surprised if you could get away with it. Then again, the talent of people like Frank Abagnale is to get people to do what they normally would not.

Post 9/11, just to even try this, you'd be facing a heck of a long time in prison - probably not a very nice one either!

@Manfred I've come to the conclusion that to provide a real answer either way, I would have to invoke SSI and I don't feel it is responsible to do so.  I started a meta Q http://meta.aviation.stackexchange.com/questions/258/are-questions-that-involve-ssi-on-topic to discuss if Q's like that are on-topic as any substantive answer must involve SSI (to justify a NO or to explain a YES).

On short distance airliners in Eastern Europe in the '70s, passengers, even with children, could sometimes visit the cabin in-flight, if they asked nicely, and the captain was in a good mood. Those times are long gone.

A lot has changed since the Frank Abagnale / "Catch Me If You Can" days, and riding as a non-revenue passenger (particularly in the cockpit jump seat) is no longer not as simple as grabbing a passable captain's uniform, polishing your shoes up, and smooth-talking the flight crew.
Someone seeking a ride in an airplane jump seat would still have to pass through airport security and prove their identity & authorization to occupy such a seat to the satisfaction of the crew operating the flight, which would likely include checking credentials that are at lease somewhat difficult to forge.
So in short it's possible – if someone is particularly adept at social engineering, forgery, and has at least a working knowledge of airport & airline security procedures they might get away with it – but it's extremely unlikely, and as has been pointed out the consequences if and when you get caught are particularly unpleasant these days.

In pre-9/11 days, I was a grad student doing research on pilots.  I had a letter from the president of a major airline authorizing me to sit in the jumpseat.  That letter, and my pilots license, were enough to get me through security, on the airplane and into the jumpseat anytime.  But, things are different now.

Absolutely not, if by “sit in the cockpit” you mean after the door is closed, during the flight, at least on scheduled airline flights in the United States.
Airlines verify the identity and employment status of would-be jumpseat passengers not only through documents presented by the passenger, which might—as mentioned in another answer—be forged, stolen, or or out of date, but also through databases like the Cockpit Access Security System (CASS), operated by Rockwell Collins. CASS includes the names and photographs of crew members from each participating airline, and entries are deleted immediately if a crew member’s employment ends.
(I appreciate others’ concern about disclosure of sensitive security information, but please note that everything in this answer is from public-domain sources, and I am not a “covered person” under the relevant regulations, 49 CFR 1520.)

in addition, I'd not be at all surprised if they get lists of any non-revs approved for the flight, and anyone not on the list gets turned away instantly. They also will recognise any uniform of operators they regularly encounter (which means anyone flying from the place they're at when you attempt to break in this way) and call security when someone walks up and demands to be let on the aircraft without papers who's not recognised.

Does this apply across regions and airlines or is limited to only the US?


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Are airport employees security checked?
Is your average ramp or store employee at an international airport security checked before they are allowed to enter the gate side area or apron?

Followed shortly thereafter by are the TSA agents screened before starting screening...

No, because if airline and field operators treated their employees the way they treat their customers, the employees would unanimously quit.

@A.I.Breveleri more directly, a maintenance guy with a wrench and a screwdriver would have a lot of trouble in the metal detector :)

@jwenting Well, they have to pass through the same level of security screening as passengers do, in the EU. So obviously they have some way of dealing with this.

@DavidRicherby since when? I've worked at an airport (not in the secure zone though, but drove past the entrances every day) and the only "security" at the employee gate to enter airside was a guard shed where a guy waved through everyone and every vehicle who'd flash a badge of the correct colour at him. I also knew several spots where one could get airside without even that much security by just walking through a gap between buildings. And that was a major international airport in the EU.

@jwenting Since 2004, according to this European Union press release.

@DavidRicherby ok, that was around the time I worked there, so may have been just before the new rules were implemented.

Many employees are not screened. This article, written in the aftermath of the LAX "dry ice bomb" incident, goes in detail about the levels of security employees face.

Ramp workers like 28-year-old Dicarlo Bennett, who was charged Thursday with two counts of possessing a destructive device in a public place, have access to just about anywhere in the airport. And though they must pass a 10-year background check before they’re hired, airport workers generally do not need to clear security when they arrive for their shifts.
...
Melendez said it’s not possible to check every employee when they arrive each day, especially when many of those workers have access to potentially dangerous or disruptive items once they’re on the job. (Dry ice is regularly used by caterers to keep food cold.)
...
Arif Alikhan, deputy executive director for homeland security at LAX, said the key is to have many layers of security. He said unannounced security checks are common, and inspectors might take a look at an employee’s lunch box or bags. Employees are asked to question who enters secure areas of the airport, and told to never hold doors open for each other.

After another incident in which employees smuggled firearms and drugs onto a Puerto-Rican bound flight, the Department of Homeland Security did a feasability study on 100% employee screening. Part of their findings were:

The concept of 100% airport employee screening is feasible. However, we do not believe it is realistic at this time. Regardless of the amount of funding, resources, and effort allocated toward this endeavor, vulnerabilities will persist. While the intelligence, screening, and law enforcement communities continue to make progress in addressing these vulnerabilities, 100% airport employee screening cannot entirely bridge existing gaps. As TSA changes its regulatory requirements, technology improves, and airports upgrade existing security measures, implementing this concept would be more realistic and should be revisited.

If you do a Google search on the subject, you will find numerous documents from large airports across the country detailing their procedures, most of which merely have to do with background checks and security badges.

That depends where in the world you are. In the UK, airport employees have had to go through the same type of security checks as passengers every time they enter secure areas of the airport since the early 1990s. The rest of the European Union adopted similar measures in 2004 (source: BBC).
According to the report linked from SSumner's answer the US decided seven years ago that it would be "feasible" to make employees go through security checks, too, but they still haven't done so.


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How frequent are TCAS resolution events?
The question is a little open, but I'm wondering how many TCAS resolutions (i.e. the serious type) occur every week or month over sizeable region like the United States or Europe.

doing a search on "tcas" on avherald show quite a few

This site shows events on a map. It's hard get an idea of how often they happen but you can see the where and when.

In 4 years of flying I had many TAs but only 1 RA.

I found a very interesting paper from 2007 that analyzed TCAS performance. They analyzed recorded data to come up with 1 RA per 116 flight hours.

Over this time period, monitoring took place for approximately 190
  days, and roughly 200,000 Mode S flight hours were observed within the
  sensor’s 60 nmi coverage area. We observed a total of 1725 RA events,
  corresponding to an average of 9 RAs per day, or approximately one RA
  every 116 flight hours.

They explain that the data was taken in the Boston area, so the high amount of traffic contributes to the high number of RAs.
This thread on Airliners.net suggest differently, at least in the sense that for those pilots it is a matter of a few over years, depending on where they typically fly.